The invention relates to a side impact protection system for vehicles.
Such a protection system comprises an inflatable gas bag and a gas source such as a gas generator for inflating the gas bag. The gas bag is inflated within a few milliseconds when the vehicle is involved in a collision, it serving the vehicle occupant as an impact cushion primarily in protecting the head region, in particular in the case of a side collision. In order to extend the protection to multiple collisions, in particular with regard to a scenario with an overturn of the vehicle or a follow-on crash, the wall of the gas bag is constructed so as to be air-tight to a large extent, so that the gas bag stays inflated for longer than one second, for example. In such a case, however, the impulse of a part of the body penetrating into the gas bag is returned almost completely, as the gas bag constitutes an elastic cushion. A damping of the impact by controlled escaping of the filling gas through a relief opening is out of the question, if the useful life of the gas bag is to be preserved.
The invention thus provides a side impact protection system by which, on the one hand, the kinetic energy of the part of the body penetrating into the gas bag on an impact of the occupant can be depleted whilst, however, maintaining the protective function for the occupant for the duration of a complex course of a crash. This is achieved by a protection system of the aforementioned kind in that at least one burst chamber is provided which is separated in its contour shape from the inflatable volume of the gas bag by retaining means and the retaining means of the burst chamber are dimensioned as regards their strength such that the burst chamber is opened towards the inflatable volume of the gas bag once a predetermined value of the gas bag internal pressure, which is lower than the filling pressure of the filling gases provided by the gas source, has been attained.
Only by the overpressure which arises on a severe penetration of a part of the body into the inflated gas bag, the burst chamber is opened, enabling gas to flow into the hitherto empty burst chamber. As a result of this, the kinetic energy of the penetrating part of the body is depleted whilst the amount of gas in the gas bag is maintained as a whole so that the gas bag remains available for subsequent actions. Since the severity of impact and thus the compression of the gas bag resulting in opening of the burst chamber(s) is also a function of e.g. weight and seating position of the occupant, a protective function is thus attained which takes into account these parameters. Accordingly, impact of a heavy occupant on the gas bag may necessitate the opening of several burst chambers to intercept impact, whereas in the case of a lighter occupant impacting the gas bag at the same velocity it may possibly prove sufficient to open only a single chamber due to the lesser impulse involved.
The embodiment of the gas bag in accordance with the invention results in the further advantage that the risk of the gas bag tearing at extremely high temperatures, involving a stronger expansion of the gas, is diminished due to the possibility of compensating the overpressure by opening one or more burst chambers. Thereby, the volume of the gas bag can be reduced so that even at extremely low temperatures the gas bag is sufficiently filled to offer protection to the occupant.
Apart from those already cited no additional parts proving a nuisance or complicating the system are needed for these enhanced protective functions. Even the accommodation space for the folded gas bag has not to be enlarged.
Preferably the gas bag comprises several burst chambers differing in size, which are opened staggered in time when a part of the body penetrates the gas bag. In this arrangement the various chambers can be configured such that they rip open at differing values of the internal pressure of the gas bag, the values each being exactly predeterminable. By a suitable arrangement of the chambers in the gas bag a protective function can thus be achieved which is optimally adapted to the seating position and impact severity of the vehicle occupant, namely just as many burst chambers of the gas bag then being opened in the region of the point of impact as are needed to intercept the impact as best possible. Accordingly, the above-mentioned individual parameters of a vehicle occupant, such as size, weight and seating position are even better taken into account on making use of the gas bag side impact protection device.
It is of advantage to form the burst chambers with tear seams or alternatively with a bond to permit a defined opening response of the chambers.